The preset invention relates to an image pickup apparatus, and is preferably utilized to take an image of blood vessels inside a living body for authentication, for example.
Biometric authentication uses blood vessels as a target of authentication. Since the main absorbers of Near-InfraRed (NIR) light in the blood vessels are deoxy-hemoglobin (venous blood) and oxy-hemoglobin (arterial blood), an image pickup device, which is for example disclosed in Jpn. Pat. Appln. Laid-open Publication No. 2004-135609 (FIGS. 1, 3 and 10), can take an image of the blood vessels by utilizing the characteristics of NIR light.
This kind of image pickup device has NIR light sources on the surface of its housing. The NIR light sources emit NIR light to a finger placed on an image pickup aperture. In this case, the NIR light has higher intensity than ordinary light in the atmosphere (the ordinary light includes visible light around the finger). The NIR light goes into the finger and then comes out from the pad of the finger. This NIR light is led to an imaging plane of a Charge Coupled Device (CCD) via an optical lens and an ultraviolet filter to project the blood vessels.
The image pickup device then utilizes photoelectric transducers on the imaging plane of the CCD to perform photoelectric conversion. This increases/decreases electric charges in the CCD per unit time to improve the imaging sensitivity of the CCD to the NIR light.
This image pickup device does not have any physical shields to shut out ordinary light, because it can electrically reduce noise generated from ordinary light. Therefore, the image pickup device can be small.